Nano-sized materials come into the limelight these days because of their excellent electrical, optical, and mechanical properties. The research that has been being so far progressed about the nano structure shows a possibility as advanced materials for the optical devices based on the new phenomenon like the quantum size effect. Particularly, in case of the nano wire, it is highlighted as the new optical device materials as well as a single electron tunneling device.
The carbon nanotube, as a typical example of the nano wire, is in a tubular form and has a structure in which one carbon atom is covalently bonded to other carbon atoms in hexagonal honeycomb structure. The diameter of the carbon nanotube is exceedingly small to a nano-scale. Particularly, this carbon nanotube is known as a perfect material which nearly does not have any defect among the existing materials and which has a remarkable characteristic in the mechanical property, the electrical selectivity, the field emission or the high-efficiency hydrogen storage.
Recently, high performance bimolecular sensors have been developed by using the nano wire like the carbon nanotube. The reason why the nano wire like the carbon nanotube is used for a biosensor is that a labeling for optical measurement is not required and a reaction can be created in the water phase without the deformation of a protein. That is, a fluorescent material, an isotope, or the like has been used for detecting the reaction results in a conventional biomolecule sensing method; however, the materials such as the fluorescence or the isotope are very harmful to the human body and the detection procedure is moreover complicate. If the electrical characteristic of the nano wire is used at the time of detection, it has an advantage that it is not harmful to health and it can exactly detect the reaction results.
However, in the conventional biosensor using the existing nano wire or the carbon nanotube, there is a problem in that the resistance increases, the electrical characteristic is degraded, and the detection sensitivity is also degraded consequently, especially in binding a material, which can directly react on the nano wire or the carbon nanotube, with a biomaterial. Moreover, there is a problem in that the electrical characteristic of each nano wire is transformed at the time of plating a polymer layer on a surface of the nano wire or directly immobilizing the biomaterial on the surface of the nano wire through a linker molecule.
Therefore, a demand for a high sensitivity biosensor, in which the electrical characteristic is not degraded, has increased with the excellent and convenient electrical characteristics of the nano wire.
Meanwhile, with the development of the food industry, the many kinds of processed foods appear recently. Accordingly, the kind and consumption of an additive used for the food expands more and more. The food additive is inevitably used for processing and preserving the foods; however, the secure of the safety should be austerely held in high repute, because the food additive itself, strictly speaking, is not a food ingredient and a little amount thereof is continuously taken through the foods for a lifetime. Even though general consumers have an interrogation or an anxiety about the food additive, most of them do not know whether what kinds of the foods have the food additive and how much the additive is safe for health. Therefore, a method for easily confirming whether there is the food additive in the foods is gradually required.